ISWC 2023

For the 9th consecutive year, metaphacts is a Gold sponsor of the International Semantic Web Conference (ISWC2023), taking place November 6-10 in Athens, Greece.


Accepted papers


Knowledge Graph Injection for Reinforcement Learning

Robert Wardenga, Liubov Kovriguina, Dmitrii Pliukhin, Daniil Radyush, Ivan Smoliakov, Yuan Xue, Henrik Müller, Aleksei Pismerov, Dmitry Mouromtsev, Daniel Kudenko


In reinforcement learning (RL) an agent usually learns the specifics and rules of the environment via interaction. This limits the agent in taking the best action only from the current observation and past experience. Therefore, providing relevant external knowledge for RL agents, as well as incorporating learned knowledge in the RL process can be a critical part of agent’s successful training in real-world tasks. We propose a method, an architecture and experimental results for injecting expert knowledge in the form of RDF knowledge graphs (KGs) into the RL processes, showing how knowledge consumption increases sample efficiency. Furthermore, we investigate the scalability of our approach concerning the complexity of the underlying task showing injection of KGs is beneficial to the solution of more complex RL tasks. For experimental evaluation we used the Minigrid environment, which is a standard benchmark for RL. For this environment, we designed an ontology and generated a KG, that promotes reusability and interoperability across heterogeneous data of the environment. We show that adding knowledge to the agent's learning process improves sample efficiency and the benefits increase with the complexity of the environment.


The RML Ontology: A Community-Driven Modular Redesign After a Decade of Experience in Mapping Heterogeneous Data to RDF

Ana Iglesias-Molina, Dylan Van Assche, Julián Arenas-Guerrero, Ben De Meester, Christophe Debruyne, Samaneh Jozashoori, Pano Maria, Franck Michel, David Chaves-Fraga and Anastasia Dimou


The Relational to RDF Mapping Language (R2RML) became a W3C Recommendation a decade ago. Despite its wide adoption, its potential applicability beyond relational databases was swiftly explored. As a result, several extensions and new mapping languages were proposed to tackle the limitations that surfaced as R2RML was applied in real-world use cases. Over the years, one of these languages, the RDF Mapping Language (RML), has gathered a large community of contributors, users, and compliant tools. So far, there has been no well-defined set of features for the mapping language, nor was there a consensus-marking ontology. Consequently, it has become challenging for non-experts to fully comprehend and utilize the full range of the language’s capabilities. After three years of work, the W3C Community Group on Knowledge Graph Construction proposes a new specification for RML. This paper presents the new modular RML ontology and the accompanying SHACL shapes that complement the specification. We discuss the motivations and challenges that emerged when extending R2RML, the methodology we followed to design the new ontology while ensuring its backward compatibility with R2RML, and the novel features which increase its expressiveness. The new ontology consolidates the potential of RML, empowers practitioners to define mapping rules for constructing RDF graphs that were previously unattainable, and allows developers to implement systems in adherence with [R2]RML.